Many factors affect a golfer's ability to achieve a strong, solid impact on the ball. In terms of equipment, the way in which weight is distributed around the club head is an important consideration. Weight positioning affects the center of gravity of the club and is one factor that determines the “moment of inertia” or MOI of the club head. A high moment of inertia creates a more stable, solid hit and a club head that is less prone to twisting.
With regard to putting, in particular, many factors affect performance, including developing a good stroke and “reading the greens.” But as with other clubs, it is important to hit the ball with the ‘sweet spot’ of the putter face. Regardless of putting stroke, reading the greens or practice, if the golfer strikes the ball off the sweet spot of the putter face, consistently good results will not be achieved. Putts struck with anything other than the sweet spot may cause putter-face rotation or wobble and, as a consequence, less energy will be imparted to the ball and/or it will roll offline The rotation may be so minimal that the golfer is not even aware of it, though wobble may lead to a slight vibration in the golfer's hands.
Moving weight to the different places also can make the “sweet spot” larger. A larger sweet spot means a larger hitting area which translates to more solid contact and greater distance. However, to maintain a proper swing weight (the perceived heaviness of the club), the overall weight of the head must remain about the same. Thus, to achieve a larger sweet spot, mass from behind the face must be taken out and moved to the perimeters of the club. This process creates an empty cavity behind the face and led to the name “cavity back” iron.
Putting extra weight out at the heel, sole, top line and the toe is the major factor in creating a larger MOI and more forgiveness. This design, called perimeter weighting, has been a game-improver for many high handicap golfers, with fewer golfers using the harder to hit “blade” style clubs.
With a thick top line, balls hit high on the club face will still be solid and maintain proper distance. A wide sole may create a lower center of gravity, thereby achieving a higher shot. A wider sole also has less of a tendency to dig into the turf, leading to fewer “fat shots.” A wide sole also has a better chance of getting through rough and the sand.
Even with relativity recent improvements such as perimeter weighting, the face of any club head includes an area considered to be the sweet spot for that club. Any device that would allow a golfer to consistently strike the ball in this area should improve performance, and would therefore be welcomed by the golfing community.